Waste from slaughterhouses dumped by the riverside.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/plight-periyar
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/new-indian-express-kochi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/slaughter-waste
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/periyar
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-quality
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/drinking-water
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/state-pollution-control-board-spcb
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/kerala